3D printing all-solid-state lithium ion battery negative electrode for energy storage and preparation method thereof

Abstract

The invention discloses a 3D printing all-solid-state lithium ion battery negative electrode for energy storage and a preparation method thereof, and relates to the technical field of solid-state batteries. The 3D printing lithium ion battery negative plate comprises a current collector, wherein a first 3D printing layer and a second 3D printing layer are sequentially arranged on the current collector; wherein the first 3D printing layer is composed of a structure unit and a gap unit; the second 3D printing layer covers the first 3D printing layer; the first 3D printing layer and the second 3D printing layer respectively comprise a silicon-based material and / or a hard carbon material. According to the 3D printing lithium ion battery negative plate, the negative electrode with the porous structure is combined with the chemical stability of the silicon-based material and / or the hard carbon material layer on the negative electrode, so that the technical problems of poor solid-solid interface contact and volume expansion of an electrode material of an existing all-solid-state battery are solved. The preparation method solves the interface contact problem of a traditional coating process, does not need to depend on a high-cost surface modification technology, reduces the process cost and is suitable for large-scale production.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and specifically relates to a 3D-printed all-solid-state lithium-ion battery negative electrode for energy storage and a preparation method thereof. Technical Background

[0002] All-solid-state batteries (ASSBs) are considered a core development direction for next-generation energy storage technology due to their significant advantages, including high energy density, intrinsic safety, and a wide electrochemical window. They hold broad application prospects in electric vehicles, portable electronic devices, and large-scale energy storage. However, despite their superior theoretical performance, the practical application of all-solid-state batteries still faces a series of technical bottlenecks, particularly poor solid-solid interface contact and volume expansion of electrode materials.

[0003] Specifically, the planar electrodes prepared by the traditional coating process are difficult to achieve close fit with the solid electrolyte due to rigid contact, and microscopic gaps or defects are easily formed at the interface, resulting in a significant increase in the interfacial impedance and a significant reduction in the lithium ion transmission efficiency, thereby affecting the battery's rate performance and energy efficiency. In addition, although high-capacity electrode materials represented by silicon-based negative electrodes have a theoretical specific capacity of up to 3579mAh / g, they easily cause particle pulverization, active material shedding, and mechanical failure of the solid electrolyte interface (SEI) due to a volume expansion of more than 300% during the lithium insertion / delithiation process, which leads to a decrease in the stability of the electrode-electrolyte interface and a rapid decay of the cycle capacity.

[0004] Solving these key problems requires not only breakthroughs in the microstructural design of electrode materials and solid-state electrolytes, but also multi-dimensional innovations such as interface modification technology, composite electrolyte systems, and new electrode preparation processes, so as to achieve the leap from laboratory research to large-scale commercial application of all-solid-state batteries.

[0005] In response to these problems, the existing technology has proposed a variety of improvement schemes, but there are still significant limitations. For example, the use of atomic layer deposition (ALD) technology to construct a nano-scale coating on the electrode surface can effectively improve the wettability between the electrode and the solid electrolyte and reduce the interfacial impedance, but it relies on high vacuum equipment, the process is complex and the cost is high, making it difficult to meet the needs of large-scale industrial production; In addition, by designing a nanoporous silicon structure to alleviate the volume expansion problem of the silicon-based negative electrode during the lithium insertion / delithiation process, although the structural stability of the electrode is improved to a certain extent, the high specific surface area exacerbates the side reactions between the electrode and the electrolyte, resulting in the accumulation of interfacial byproducts and the attenuation of electrochemical performance; In addition, during the cycle, the mechanical stress generated by the volume change between the electrode and the electrolyte continues to accumulate, which can easily cause the expansion and delamination of interfacial microcracks, which not only further increases the interfacial impedance, but also provides a channel for the growth of lithium dendrites, significantly increasing the short circuit risk of the battery.

[0006] These intertwined technical challenges have collectively constrained the industrialization of all-solid-state batteries. Therefore, an innovative solution that balances interface optimization, structural stability, and process feasibility is urgently needed. Summary of the Invention

[0007] In response to the problems in the prior art, the present invention proposes a 3D-printed all-solid-state lithium-ion battery negative electrode for energy storage and a preparation method thereof, which solves the technical problems of poor solid-solid interface contact and volume expansion of electrode materials in existing all-solid-state batteries.

[0008] To solve the above technical problems, in the first aspect, the present invention provides a 3D-printed lithium-ion battery negative electrode sheet, comprising a current collector, on which a first 3D-printed layer and a second 3D-printed layer are sequentially provided; wherein, the first 3D-printed layer is composed of a structural unit and a void unit; the second 3D-printed layer is covered on the first 3D-printed layer; the first 3D-printed layer and the second 3D-printed layer respectively contain silicon-based materials and / or hard carbon materials.

[0009] Furthermore, the first 3D printing layer and the second 3D printing layer are single material layers of silicon-based material layers or hard carbon material layers respectively.

[0010] Furthermore, the first 3D printing layer is a silicon-based material layer; and the second 3D printing layer is a hard carbon layer.

[0011] Furthermore, when the first 3D printed layer is a silicon-based material layer and the second 3D printed layer is a hard carbon layer, the thickness of the structural unit after being covered with the second 3D printed layer is d1, and the thickness of the gap unit after being covered with the second 3D printed layer is d2, wherein d2≤d1, preferably d2<d1.

[0012] Furthermore, in the first 3D printed layer, the spacing between adjacent gap units is 0.8 to 1.3 mm; the total area of ​​the gap units accounts for 13% to 20%; the thickness of the structural unit after covering the second 3D printed layer is d1, and the difference between d1 and d2 is 10 μm to 30 μm.

[0013] Furthermore, the distance between adjacent gap units is 0.8-1 mm, preferably 1 mm.

[0014] Furthermore, the total area of ​​the void units accounts for 13% to 17%, more preferably 15% to 17%, and even more preferably 17%.

[0015] Furthermore, the difference between d1 and d2 is 10 μm to 20 μm, and more preferably 20 μm.

[0016] Furthermore, the structural units are connected to form a honeycomb shape, a concentric ring shape, an Archimedean spiral shape, a parallel line shape, a parallel wavy line shape or a Heber curve shape; preferably a honeycomb shape.

[0017] Furthermore, the silicon-based material includes at least one of micron silicon, porous silicon, amorphous silicon, and silicon-oxygen composite materials, preferably micron silicon.

[0018] Furthermore, the current collector is copper foil or copper-lithium composite tape, preferably copper-lithium composite tape.

[0019] Furthermore, the 3D printed layer is obtained by printing and drying with a 3D printer; wherein, the structural unit is obtained by 3D printing using a first slurry obtained by mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent; and the second 3D printed layer is obtained by 3D printing using a second slurry obtained by mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent.

[0020] Furthermore, the binder includes at least one of hydrogenated nitrile rubber, nitrile rubber, carboxyl nitrile rubber, butadiene rubber, and polyisobutylene rubber; preferably hydrogenated rubber; the binders in the first slurry and the second slurry are the same or different.

[0021] Furthermore, the organic solvent includes at least one of xylene, toluene, anisole, heptane, butyl butyrate, and hexyl butyrate, preferably p-xylene; and the organic solvents in the first slurry and the second slurry are the same or different.

[0022] In a second aspect, the present invention further provides a method for preparing a printed lithium-ion battery negative electrode, comprising the following steps:

[0023] (1) mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent to obtain a slurry; and passing the slurry into a 3D printer syringe pump;

[0024] (2) performing 3D printing on the current collector using a 3D printer to obtain a first 3D printed layer and a second 3D printed layer; wherein the first 3D printed layer includes a structural unit obtained by printing the slurry and a gap unit; and a second 3D printed layer is obtained by printing the slurry on the first 3D printed layer;

[0025] (3) The material after 3D printing is dried to obtain the 3D printed lithium-ion battery negative electrode sheet.

[0026] As a further solution, the mass ratio of the silicon-based material and / or hard carbon material to the binder in the slurry is (18-20):1, preferably 19:1.

[0027] As a further solution, the 3D printer's extrusion pressure is 0.01-0.05 MPa, and the printing speed is 100-500 mm / s. The printer's extrusion pressure is maintained at 0.01-0.05 MPa, ensuring uniform extrusion and close contact with the substrate, avoiding uneven electrode thickness or local collapse due to pressure fluctuations. Simultaneously, the printing speed is controlled at 100-500 mm / s, working in conjunction with the pressure parameters to ensure the slurry is formed with a stable flow rate and shape, preventing stringing and breakage due to excessive speed, or uneven accumulation due to excessive speed. This dual, precise control of pressure and printing speed ensures highly consistent thickness and honeycomb structure dimensions of the printed electrode. Furthermore, the spacing between the interstitial cells and the total area of ​​the interstitial cells can be conveniently controlled to 13%-20%, reserving sufficient channels for rapid lithium ion transport while ensuring the electrode has good mechanical strength and active material loading capacity, effectively improving the overall electrochemical performance of the negative electrode.

[0028] As a further solution, the drying treatment includes first drying at 50-80° C. for 20-40 minutes, and then vacuum drying at 75-85° C. for 10-24 hours.

[0029] As a further solution, the slurry compositions of the first 3D printing layer and the second 3D printing layer may be the same or different.

[0030] As a further solution, the first 3D printing layer and the second 3D printing layer are single material layers of silicon-based material layers or hard carbon material layers respectively.

[0031] As a further solution, the first 3D printing layer is a silicon-based material layer; and the second 3D printing layer is a hard carbon layer.

[0032] As a further solution, when the first 3D printed layer is a silicon-based material layer and the second 3D printed layer is a hard carbon layer, the thickness of the structural unit after being covered with the second 3D printed layer is d1, and the thickness of the gap unit after being covered with the second 3D printed layer is d2, wherein d2≤d1, preferably d2<d1.

[0033] As a further solution, in the first 3D printing layer, the spacing between adjacent gap units is 0.8 to 1.3 mm; the total area of ​​the gap units accounts for 13% to 20%; and the difference between d1 and d2 is 10 μm to 30 μm.

[0034] As a further solution, the spacing between adjacent gap units is 0.8 to 1 mm, preferably 1 mm.

[0035] As a further solution, the total area of ​​the void units accounts for 13% to 17%, more preferably 15% to 17%, and even more preferably 17%.

[0036] As a further embodiment, the difference between d1 and d2 is 10 μm to 30 μm, more preferably 10 μm to 20 μm, and even more preferably 20 μm.

[0037] As a further solution, the structural units are connected to form a honeycomb shape, a concentric ring shape, an Archimedean spiral shape, a parallel line shape, a parallel wavy line shape or a Heber curve shape, preferably a honeycomb shape.

[0038] As a further solution, the silicon-based material includes at least one of micron silicon, porous silicon, amorphous silicon, and silicon-oxygen composite materials, preferably micron silicon.

[0039] As a further solution, the current collector is copper foil or copper-lithium composite tape, preferably copper-lithium composite tape.

[0040] As a further solution, a solid electrolyte layer is provided on the surface of the negative electrode of the battery.

[0041] As a further solution, the binder includes at least one of hydrogenated nitrile rubber, nitrile rubber, carboxylated nitrile rubber, butadiene rubber, and polyisobutylene rubber; preferably hydrogenated rubber.

[0042] As a further embodiment, the organic solvent includes at least one of xylene, toluene, anisole, heptane, butyl butyrate, and hexyl butyrate, preferably p-xylene.

[0043] In a third aspect, the present invention also proposes a lithium-ion battery, an electrochemical device, and an energy storage device comprising the above-mentioned 3D printed lithium-ion battery negative electrode sheet or a negative electrode prepared using the above-mentioned 3D printed lithium-ion battery negative electrode sheet preparation method.

[0044] Furthermore, the lithium-ion battery is an all-solid-state battery, and the pressure of the all-solid-state battery is 100-300 MPa, preferably 250 MPa. When the battery is an all-solid-state battery, the surface of its negative electrode is covered with a solid electrolyte layer.

[0045] Compared with the prior art, the present invention has at least the following beneficial effects:

[0046] (1) The present invention constructs a first 3D printing layer including structural units and void units through 3D printing technology to obtain a negative electrode with a porous structure. The periodic pores obtained by 3D printing not only improve the conductivity but also reserve space for the lateral volume expansion of the silicon material (expansion parallel to the direction of the electrode), thereby alleviating the pulverization problem and enhancing the interface contact between the electrode and the solid electrolyte.

[0047] (2) By uniformly coating the second 3D printed layer on the first 3D printed layer, a composite protection mechanism of silicon-based material or hard carbon material coating is established to inhibit the SEI rupture caused by the volume change of silicon particles during the cycle, reduce the shedding of active materials, and reduce the risk of lithium dendrite growth; in addition, it is preferred that there is a thickness difference between d1 and d2, which not only further improves the conductivity, but also reserves the volume expansion space of the material in the direction perpendicular to the electrode, thereby synergistically improving the cycle performance, rate performance and high and low temperature performance of the battery.

[0048] (3) By combining the chemical stability of the 3D-printed porous structure negative electrode with the silicon-based material or hard carbon material layer, the ion transfer efficiency at the electrode-electrolyte interface is significantly improved, the interfacial impedance is reduced, and the structural integrity of the long-term cycle is maintained.

[0049] (4) The lithium-ion battery comprising the 3D-printed lithium-ion battery negative electrode sheet of the present invention has unique effects in terms of interface contact quality (low internal resistance) and safety (dendrite inhibition), and shows significant advantages in terms of rate performance, cycle stability, voltage platform stability, capacity retention, discharge capacity and first efficiency. It has excellent temperature adaptability, high and low temperature performance and high load performance, and is suitable for use in various environments and application conditions.

[0050] (5) The preparation method of the 3D printed lithium-ion battery negative electrode sheet of the present invention solves the interface contact problem of the traditional coating process, and does not need to rely on high-cost surface modification technology, thereby reducing process costs and being suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0052] Figure 1 This is a schematic diagram of the structure of a 3D printed lithium-ion battery negative electrode sheet of the present invention;

[0053] Figure 2 Figure 3 shows different patterns of the 3D-printed lithium-ion battery negative electrode sheet of the present invention. Figure (a) shows an Archimedean spiral, Figure (b) shows a parallel wavy line, Figure (c) shows a Heber curve, and Figure (d) shows a honeycomb. Note that for simplicity, only the first 3D printed layer is shown.

[0054] Figure 3 The figures show the rate performance test (Figure a), cycle performance test (Figure b), long cycle performance test (Figure c), charge and discharge cycle performance at different temperatures (from -5°C to 75°C) (d), charge and discharge curves at different temperatures (e), and charge and discharge curves of the lithium ion battery under different loads (30 mg, 50 mg, and 100 mg) prepared in Example 6;

[0055] Figure 4 Graphs showing the cycling performance of lithium-ion batteries prepared in Example 6 (labeled as Li-Si-C-Honeycomb in the figure) and Comparative Example 7 (labeled as Li-Si-C-Cover in the figure);

[0056] Figure 5 Electrochemical impedance spectra of the lithium-ion batteries prepared in Example 6 (labeled as Li-Si-C-Honeycomb in the figure) and Comparative Example 7 (labeled as Li-Si-C-Cover in the figure) during full cell cycling;

[0057] Figure 6 Comparative SEM and DES images of the negative electrode and solid electrolyte of the battery of Example 6 (labeled as Li-Si-C-Honeycomb in the figure) and Comparative Example 7 (labeled as Li-Si-C-Cover in the figure);

[0058] Figure 7 The figures show the change in specific capacity and coulombic efficiency of the lithium-ion batteries of Example 6 (labeled as Li-Si-C-Honeycomb in the figure) and Comparative Example 7 (labeled as Li-Si-C-Cover in the figure) during multiple charge and discharge cycles;

[0059] Figure 8 The cycling performance test graphs of the lithium-ion batteries of Example 6 (labeled as Li-Si-C-Honeycomb in the figure), Comparative Example 7 (labeled as Li-Si-C-Cover in the figure), Comparative Example 8 (labeled as Li-Si-Honeycomb in the figure), and Comparative Example 9 (labeled as Li-Si-Cover in the figure) are shown. DETAILED DESCRIPTION

[0060] For ease of understanding, the present invention will be described in more detail below, and examples of the present invention are given, but the scope of the present invention is not limited thereby.

[0061] The following is a description of terms or words, and unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0062] In a first aspect, the present invention provides a 3D-printed lithium-ion battery negative electrode sheet, comprising a current collector, on which a first 3D-printed layer and a second 3D-printed layer are sequentially provided; wherein the first 3D-printed layer is composed of a structural unit and a void unit; the second 3D-printed layer is covered on the first 3D-printed layer; the first 3D-printed layer and the second 3D-printed layer respectively contain silicon-based materials and / or hard carbon materials.

[0063] In order to solve the problems of poor solid-solid interface contact and volume expansion of electrode materials in existing all-solid-state batteries, as well as the problems of complex process and high cost, the technical solution of the present invention constructs a periodic pore structure on the surface of the current collector through 3D printing technology. The structural units and the void units in the first 3D printing layer are arranged at intervals to provide a buffer space for the volume expansion of silicon during battery operation, alleviate the pulverization problem, and provide a three-dimensional interpenetrating ion transport network to enhance the interface contact between the electrode and the solid electrolyte; further, the present invention coats a silicon-based material layer and / or a hard carbon material on the first 3D printing layer. The material layer realizes surface chemical passivation and mechanical reinforcement, which can inhibit the SEI rupture caused by the volume change of silicon particles during the cycle, thereby reducing the shedding of active materials and reducing the risk of lithium dendrite growth, and ultimately achieving high-stability interface contact and long cycle life of lithium-ion batteries; in addition, the embodiments of the present invention and comparative examples confirm that the silicon negative electrode with porous characteristics obtained by 3D printing technology is combined with the chemical stability of the silicon-based material layer or the hard carbon material layer, which significantly improves the ion transfer efficiency of the electrode-electrolyte interface, reduces the interface impedance, and maintains the structural integrity of long-term circulation, thereby realizing the coordinated optimization of the interface and structure.

[0064] The technical solution of the present invention adopts 3D printing technology to directly solve the interface contact problem of traditional coating process. It does not need to rely on high-cost surface modification technology (such as ALD) and does not require complex equipment. It can reduce process costs and is compatible with large-scale production.

[0065] As a further solution, the first 3D printing layer and the second 3D printing layer are single material layers of silicon-based material layers or hard carbon material layers respectively.

[0066] As some optional parameters, the first 3D printing layer is a silicon-based material layer; the second 3D printing layer is a hard carbon layer.

[0067] As some optional parameters, when the first 3D printed layer is a silicon-based material layer and the second 3D printed layer is a hard carbon layer, the thickness of the structural unit after being covered with the second 3D printed layer is d1, and the thickness of the gap unit after being covered with the second 3D printed layer is d2, wherein d2≤d1, preferably d2<d1.

[0068] As a further solution, in the first 3D printing layer, the spacing between adjacent gap units is 0.8 to 1.3 mm; the total area of ​​the gap units accounts for 13% to 20%; and the difference between d1 and d2 is 10 μm to 30 μm.

[0069] It should be noted that the present invention adopts 3D printing technology that can print periodic patterns. The spacing of the gap units in the present invention refers to the straight-line distance between the center lines or center points of adjacent gap units.

[0070] As some optional parameters, the spacing between adjacent gap units is 0.8-1 mm, preferably 1 mm.

[0071] As some optional parameters, the total area of ​​the gap units accounts for 13% to 17%, preferably 15% to 17%, and more preferably 17%.

[0072] As some optional parameters, the difference between d1 and d2 is 10 μm to 20 μm, and more preferably 20 μm.

[0073] As a further solution, the structural units are connected to form a honeycomb shape, a concentric ring shape, an Archimedean spiral shape, a parallel line shape, a parallel wavy line shape or a Heber curve shape. Figure 2 Examples are shown in which the first 3D printing layer is in the shape of an Archimedean spiral, a parallel wavy line, a Heber curve, and a honeycomb.

[0074] As some optional parameters, the structural units are connected to form a honeycomb shape.

[0075] As a further solution, the silicon-based material includes at least one of micron silicon, porous silicon, amorphous silicon, and silicon-oxygen composite materials.

[0076] As some optional parameters, the silicon-based material is micron silicon.

[0077] As a further solution, the current collector is copper foil or copper-lithium composite tape.

[0078] As some optional parameters, the current collector is a copper-lithium composite ribbon. Optionally, the copper-lithium composite ribbon is a lithium-plated copper ribbon, a pressed composite copper-lithium ribbon, a lithium-coated copper ribbon, a multilayer composite copper-lithium ribbon, or an alloy copper ribbon.

[0079] As a further solution, a solid electrolyte layer is provided on the surface of the negative electrode of the battery. Understandably, when d2 is less than d1, the area of ​​the void unit covered by the second 3D printed layer forms a depression compared to the area of ​​the structural unit covered by the second 3D printed layer, and the depression area will be filled with a solid electrolyte at this time. As some optional solutions, the solid electrolyte layer is adhered to the surface of the negative electrode of the battery under pressure. As a further solution, the 3D printed layer is obtained by printing and drying with a 3D printer; wherein, the structural unit is obtained by 3D printing using a first slurry obtained by mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent; and the second 3D printed layer is obtained by 3D printing using a second slurry obtained by mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent.

[0080] As some optional parameters, the binder includes at least one of hydrogenated nitrile rubber, nitrile rubber, carboxyl nitrile rubber, butadiene rubber, and polyisobutylene rubber;

[0081] As some optional parameters, the binder is hydrogenated rubber.

[0082] As some optional parameters, the binders in the first slurry and the second slurry are the same or different.

[0083] As some optional parameters, the organic solvent includes at least one of xylene, toluene, anisole, heptane, butyl butyrate, and hexyl butyrate.

[0084] As some optional parameters, the organic solvent is p-xylene.

[0085] As some optional parameters, the organic solvents in the first slurry and the second slurry are the same or different.

[0086] In a second aspect, the present invention provides a method for preparing a 3D printed lithium-ion battery negative electrode sheet, comprising the following steps:

[0087] (1) mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent to obtain a slurry; and passing the slurry into a 3D printer syringe pump;

[0088] (2) performing 3D printing on the current collector using a 3D printer to obtain a first 3D printed layer and a second 3D printed layer; wherein the first 3D printed layer includes a structural unit obtained by printing the slurry and a gap unit; and a second 3D printed layer is obtained by printing the slurry on the first 3D printed layer;

[0089] (3) The material after 3D printing is dried to obtain the 3D printed lithium-ion battery negative electrode sheet.

[0090] As a further optional solution, step (1) can be carried out under mixing and stirring conditions, optionally with low-speed stirring for preliminary mixing to allow the components to begin to contact and fuse; followed by high-speed stirring to facilitate the full dispersion of the components (e.g., silicon particles) in the mixed solution to form a uniform and stable slurry. The time for low-speed stirring and high-speed stirring can be set as needed, for example, stirring for about 5 to 20 minutes each.

[0091] As a further optional solution, the 3D printing process also includes model design and parameter control; the model design operation is used to design a three-dimensional model of the honeycomb structure with the help of computer-aided design (such as CAD) software; the parameter control operation is used to import the designed three-dimensional model into the 3D printer control system and set printing parameters.

[0092] As a further solution, the mass ratio of the silicon-based material and / or hard carbon material to the binder in the slurry is (18-20):1.

[0093] As some optional parameters, the mass ratio of the silicon-based material and / or hard carbon material to the binder in the slurry is 19:1.

[0094] As a further solution, the extrusion pressure of the 3D printer is 0.01~0.05Mpa. During actual operation, the extrusion pressure of the printer can be reasonably adjusted according to the fluidity of the slurry and the complexity of the honeycomb structure; the printing speed is 100~500mm / s, thereby ensuring that the slurry can be extruded from the nozzle evenly and stably to form a precise honeycomb structure.

[0095] As a further embodiment, the drying process includes drying at 50-80°C for 20-40 minutes (primary drying), followed by vacuum drying at 75-85°C for 10-24 hours (further drying). In practice, the preliminary drying process can be performed on a printer's hot plate, and the further drying process can be performed in a vacuum drying oven.

[0096] As a further solution, the first 3D printing layer and the second 3D printing layer are single material layers of silicon-based material layers or hard carbon material layers respectively.

[0097] As some optional parameters, the first 3D printing layer is a silicon-based material layer; the second 3D printing layer is a hard carbon layer.

[0098] As some optional parameters, when the first 3D printed layer is a silicon-based material layer and the second 3D printed layer is a hard carbon layer, the thickness of the structural unit after being covered with the second 3D printed layer is d1, and the thickness of the gap unit after being covered with the second 3D printed layer is d2, wherein d2≤d1, preferably d2<d1.

[0099] As a further solution, in the first 3D printing layer, the spacing between adjacent gap units is 0.8 to 1.3 mm; the total area of ​​the gap units accounts for 13% to 20%; and the difference between d1 and d2 is 10 μm to 30 μm.

[0100] It should be noted that the present invention adopts 3D printing technology that can print periodic patterns. The spacing of the gap units in the present invention refers to the straight-line distance between the center lines or center points of adjacent gap units.

[0101] As some optional parameters, the spacing between adjacent gap units is 0.8-1 mm, preferably 1 mm.

[0102] As some optional parameters, the total area of ​​the gap units accounts for 13% to 17%, more preferably 15% to 17%, and even more preferably 17%.

[0103] As some optional parameters, the difference between d1 and d2 is 10 μm to 20 μm, and more preferably 20 μm.

[0104] As a further solution, the structural units are connected to form a honeycomb shape, a concentric ring shape, an Archimedean spiral shape, a parallel line shape, a parallel wavy line shape or a Heber curve shape.

[0105] As some optional parameters, the structural units are connected to form a honeycomb shape.

[0106] As a further solution, the silicon-based material includes at least one of micron silicon, porous silicon, amorphous silicon, and silicon-oxygen composite materials.

[0107] As some optional parameters, the silicon-based material is micron silicon.

[0108] As a further solution, the current collector is copper foil or copper-lithium composite tape.

[0109] As some optional parameters, the current collector is a copper-lithium composite tape.

[0110] As a further solution, a solid electrolyte layer is provided on the surface of the negative electrode of the battery.

[0111] As some optional parameters, the solid electrolyte includes one or more of an oxide electrolyte, a sulfide electrolyte, and a halide electrolyte. As some optional parameters, the electrochemical formula of the solid electrolyte is Li 6-a PS 5-a X 1+a , where 0≤a≤1, X=Cl, Br, I.

[0112] As a further solution, the binder includes at least one of hydrogenated nitrile rubber, nitrile rubber, carboxyl nitrile rubber, butadiene rubber, and polyisobutylene rubber;

[0113] As some optional parameters, the binder is hydrogenated rubber.

[0114] As a further embodiment, the organic solvent includes at least one of xylene, toluene, anisole, heptane, butyl butyrate, and hexyl butyrate.

[0115] The present invention prefers low-polarity or non-polar solvents and binders with moderate volatility and drying speed. This helps control the drying process of the printed slurry, avoiding problems such as cracking and deformation caused by excessively fast or slow drying. This makes the printed silicon anode structure more uniform and dense, improving printing quality and efficiency. Furthermore, based on the principle of like dissolves like, the use of low-polarity or non-polar solvents and binders allows the binder to be fully dispersed and dissolved in the solvent, forming a uniform solution or slurry, facilitating precise control of material distribution and shaping during the 3D printing process.

[0116] As some optional parameters, the organic solvent is p-xylene.

[0117] In a third aspect, the present invention also proposes a lithium-ion battery, an electrochemical device, and an energy storage device comprising the above-mentioned 3D printed lithium-ion battery negative electrode sheet or a negative electrode prepared using the above-mentioned 3D printed lithium-ion battery negative electrode sheet preparation method.

[0118] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, and are not all embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0119] The chemical raw materials involved in the following examples and comparative examples are all prior art and are commercially available. The experimental devices, test devices, etc. involved in the following examples and comparative examples are all conventional devices in the art and are not particularly limited.

[0120] Example

[0121] Preparation method of 3D printed lithium-ion battery negative electrode sheet:

[0122] (1) Microsilicon, hydrogenated rubber (HNBR), and an appropriate amount of p-xylene solvent were uniformly mixed in a planetary mixer at a mass ratio of 95:5 for 10 minutes to obtain a first slurry;

[0123] (2) Hard carbon, hydrogenated rubber (HNBR), and an appropriate amount of p-xylene solvent were uniformly mixed in a planetary mixer at a mass ratio of 95:5 for 10 minutes to obtain a second slurry;

[0124] (3) Using a 3D printing device, a honeycomb silicon negative electrode is printed on the current collector (first 3D printing layer), and then a hard carbon layer is printed on the first 3D printing layer using a second slurry (second 3D printing layer);

[0125] (4) The printed material is dried to obtain the 3D printed lithium-ion battery negative electrode sheet.

[0126] Assembling the battery:

[0127] The prepared 3D-printed lithium-ion battery negative electrode sheet was placed into a molded battery. 60mg of Li5.3PS4.3Cl1.7 was weighed and placed into the mold. The negative electrode and electrolyte were pressed together at a pressure of 125MPa for 2 minutes to ensure a tight fit. On the other side, 5mg of the composite positive electrode was placed and pressed at a pressure of 500MPa for 2 minutes. The composite positive electrode was prepared by ball milling LCO, VGCF, and LPSCl in a mass ratio of 60:5:35 at 100rpm for 0.2h. The operating pressure of the assembled battery was 100-300MPa, preferably 250MPa.

[0128] This example explored the effects of the spacing between adjacent interstitial cells, the total area ratio of the interstitial cells, the difference between d1 and d2, and the current collector type on the initial coulombic efficiency and interfacial impedance of the resulting lithium-ion battery. The specific parameter control conditions and test results are shown in Table 1.

[0129] Table 1

[0130]

[0131] Combining Examples 1 to 6 with Comparative Examples 1 to 6, it can be confirmed that the first coulombic efficiency of the 3D-printed lithium-ion battery negative electrode sheet of the present invention is better. Combined with the first efficiency and interface impedance test results, it can be verified that in the first 3D-printed layer of the present invention, the spacing between adjacent void units is 0.8 to 1.3 mm; the total area of ​​the void units accounts for 13% to 20%; the thickness of the second 3D-printed layer covering the structural unit is d1, and the thickness of the void units covered by the second 3D-printed layer is d2, where the difference between d1 and d2 is 10μm to 30μm.

[0132] Furthermore, the spacing between adjacent gap units is preferably 0.8 to 1 mm, more preferably 1 mm; further, the total area of ​​the gap units is preferably 13% to 17%, more preferably 15% to 17%, and even more preferably 17%; further, further, the difference between d1 and d2 is 10 to 20 μm, preferably 10 to 20 μm.

[0133] In combination with Example 5, Example 7, and Example 8, it can be confirmed that in the 3D printed lithium-ion battery negative electrode sheet of the present invention, the structural units are connected to form a honeycomb shape, concentric ring shape, Archimedean spiral shape, parallel line shape, parallel wavy line shape or Heber curve shape, etc., preferably a honeycomb shape.

[0134] Figure 3 The rate performance test, cycle performance test and long cycle performance test of the lithium ion battery prepared in Example 6 are shown. It can be verified from the figure that the lithium ion battery containing the 3D printed lithium ion battery negative electrode sheet of the present invention has a high first coulombic efficiency (exceeding 100mAh / g at different rates and cycle numbers); even at a high rate (5C), the battery can still maintain a relatively high discharge capacity; the cycle performance test and the long cycle performance test show that after hundreds of cycles, the discharge capacity retention rate of the battery is still high; at different rates and cycle numbers, the charge and discharge curves of the battery show a stable voltage platform; the discharge capacity of the battery decays slowly and the capacity retention rate is high; good charge and discharge performance can be maintained in a wide temperature range (from -5°C to 75°C), showing excellent temperature adaptability; even at extremely low temperatures (such as -5°C) and high temperatures (such as 75°C), the battery can still maintain relatively stable charge and discharge performance; good charge and discharge performance can be maintained under different loads (30mg, 50mg, 100mg). Therefore, the lithium-ion battery containing the 3D printed lithium-ion battery negative electrode sheet of the present invention has significant advantages in rate performance, cycle stability, voltage platform stability, capacity retention rate, discharge capacity and first efficiency, and has excellent temperature adaptability, high and low temperature performance and high load performance. It is a high-performance lithium-ion battery suitable for use in various environments and application conditions.

[0135] Furthermore, the test results of Example 1, Comparative Examples 1 and 2 show that the pore spacing between adjacent void units in the first 3D printed layer is controlled within an appropriate range, which can improve the first efficiency of the lithium-ion battery and reduce the interface impedance; the increase in the pore spacing between adjacent void units in the first 3D printed layer will lead to an increase in the area of ​​a single pore, thereby reducing the number of void units per unit area, and thereby reducing the total area ratio of the void units, thereby reducing the first efficiency of the lithium-ion battery and increasing the interface impedance; if the spacing between adjacent void units is too small, it may cause the pore channel to narrow, limit the transmission of lithium ions in the electrolyte, thereby reducing the insertion / deintercalation efficiency of lithium ions, and the first efficiency may therefore be reduced. The longer lithium ion transmission path also increases the interface impedance.

[0136] Furthermore, the test results of Example 5, Comparative Examples 3 and 4 show that the difference in thickness between the first 3D printed layer and the second 3D printed layer is within an appropriate range, which is beneficial to improving the first efficiency of the lithium-ion battery and reducing the interface impedance; when 3D printing is completed, a certain space formed by the thickness difference between the structural unit and the void unit in the first 3D printed layer will be partially filled with electrolyte during the battery assembly process. The appropriate electrolyte layer thickness is beneficial to promoting the transmission of lithium ions, improving the lithium ion transmission efficiency, improving the interface contact between the electrolyte and the negative electrode material, and reducing the interface impedance; when the thickness of the first 3D printed layer (silicon negative electrode) is larger or smaller, the first efficiency will decrease, and the interface impedance will increase.

[0137] Furthermore, in combination with Example 6 and Comparative Example 7, the first 3D printing layer including structural units and void units is provided in this embodiment, which can significantly improve the initial efficiency of the prepared lithium-ion battery and effectively reduce the interface impedance.

[0138] In a further example of this embodiment, the cycle performance diagrams of the lithium ion batteries prepared in Example 6 and Comparative Example 7 were tested (eg Figure 4 ), impedance changes during full battery cycling (e.g. Figure 5 );in addition, Figure 6 The SEM and DES comparison diagrams of the lithium ion batteries prepared in Example 1.6 and Comparative Example 1.7 are shown. Figure 4-Figure 6 It can be confirmed that the lithium ion battery referred to by the 3D printed lithium ion battery negative electrode sheet in the embodiment of the present invention can still maintain a high capacity after 1000 cycles, showing excellent capacity retention ability, its impedance gradually decreases during the cycle, and the hard carbon layer on the negative electrode structure is smooth and flat; while the capacity of the battery of Comparative Example 7, which does not have the first 3D printed layer, decays faster, and its impedance first decreases and then increases, because its lithium ion transmission is slow, resulting in the growth of lithium dendrites and the appearance of voids in the hard carbon layer, thereby destroying the ion and electron transmission channels. Figure 7The specific capacity changes and Coulombic efficiencies of the lithium-ion batteries of Example 6 and Comparative Example 7 during multiple charge and discharge cycles are shown. As can be seen from the figure, the lithium-ion battery comprising a 3D-printed lithium-ion battery negative electrode sheet according to the embodiment of the present invention has significant advantages in cycle stability and specific capacity retention, and is suitable for applications requiring long cycle life and high energy density. However, the lithium-ion battery of the comparative example, which does not include the first 3D-printed layer having void units, exhibits faster specific capacity decay during cycling and has poor cycle stability.

[0139] In addition, this embodiment also tests the long cycle performance of the lithium ion batteries of Example 6 and Comparative Examples 7, 8 and 9. The test results are as follows: Figure 8 As shown. Among them, the parameter settings of Comparative Example 8 (marked as Li-Si-Honeycomb in the figure) and Comparative Example 9 (marked as Li-Si-Cover in the figure) are the same as those of Example 6. The difference is that the negative electrode in Comparative Example 8 includes a current collector and a first 3D printed layer on the current collector (printed from a slurry containing a negative electrode material, including structural units and void units); the negative electrode shown in Comparative Example 9 does not have the first 3D printed layer, and only includes a current collector and a uniformly coated silicon negative electrode layer. Figure 8 It can be confirmed that the lithium-ion battery including the 3D-printed lithium-ion battery negative electrode sheet of the embodiment of the present invention maintains good specific capacity during the cycle process, has a high initial specific capacity, and has a small decrease in specific capacity after 1600 cycles. It has obvious advantages in cycle stability and specific capacity retention, and is suitable for application scenarios requiring long cycle life and high energy density. By comparing the long cycle performance of the lithium-ion batteries of Example 6 with Comparative Examples 7, 8, and 9, it is reflected that the specific structure with porous characteristics in the 3D-printed lithium-ion battery negative electrode sheet of the present invention is combined with the chemical stability of the hard carbon layer coated on its surface, reflecting the synergistic optimization of the interface and structure.

[0140] The various technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the various technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. Although the embodiments of the present invention have been shown and described above, it can be understood that the above-described embodiments are exemplary and cannot be understood as limitations of the present invention. Those skilled in the art can change, modify, replace and deform the above-described embodiments within the scope of the present invention. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory.

Claims

1. A 3D printed lithium-ion battery negative electrode sheet, characterized in that: It includes a current collector, on which a first 3D printed layer and a second 3D printed layer are sequentially provided; wherein the first 3D printed layer is composed of a structural unit and a gap unit; the second 3D printed layer is covered on the first 3D printed layer; the first 3D printed layer and the second 3D printed layer respectively contain silicon-based materials and / or hard carbon materials.

2. The 3D printed lithium-ion battery negative electrode sheet according to claim 1, characterized in that: The first 3D printing layer and the second 3D printing layer are respectively single material layers of a silicon-based material layer or a hard carbon material layer; Preferably, the first 3D printing layer is a silicon-based material layer; the second 3D printing layer is a hard carbon layer; More preferably, when the first 3D printing layer is a silicon-based material layer and the second 3D printing layer is a hard carbon layer, The thickness of the structural unit after being covered with the second 3D printed layer is d1, and the thickness of the gap unit after being covered with the second 3D printed layer is d2, wherein d2≤d1, preferably d2<d1.

3. The 3D printed lithium-ion battery negative electrode sheet according to claim 2, characterized in that: In the first 3D printing layer, the spacing between adjacent gap units is 0.8 to 1.3 mm; the total area of ​​the gap units accounts for 13% to 20%; the difference between d1 and d2 is 10 μm to 30 μm; Preferably, the spacing between adjacent gap units is 0.8 to 1 mm, more preferably 1 mm; Preferably, the total area of ​​the void units accounts for 13% to 17%, more preferably 15% to 17%, and even more preferably 17%; Preferably, the difference between d1 and d2 is 10 μm to 20 μm, more preferably 20 μm.

4. The 3D printed lithium-ion battery negative electrode sheet according to claim 1, characterized in that: The structural units are connected to form a honeycomb shape, a concentric ring shape, an Archimedean spiral shape, a parallel line shape, a parallel wavy line shape or a Heber curve shape; preferably a honeycomb shape.

5. The 3D printed lithium-ion battery negative electrode sheet according to claim 1, characterized in that: The silicon-based material includes at least one of micron silicon, porous silicon, amorphous silicon, and silicon-oxygen composite materials, preferably micron silicon; And / or, the current collector is copper foil or copper-lithium composite tape; preferably copper-lithium composite tape; And / or, a solid electrolyte layer is provided on the surface of the battery negative electrode.

6. The 3D printed lithium-ion battery negative electrode sheet according to claim 1, characterized in that: The 3D printed layer is obtained by printing and drying with a 3D printer; wherein the structural unit is obtained by 3D printing using a first slurry obtained by mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent; and the second 3D printed layer is obtained by 3D printing using a second slurry obtained by mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent; Preferably, the binder comprises at least one of hydrogenated nitrile rubber, nitrile rubber, carboxylated nitrile rubber, butadiene rubber, and polyisobutylene rubber; preferably hydrogenated rubber; the binders in the first slurry and the second slurry are the same or different; Preferably, the organic solvent includes at least one of p-xylene, toluene, anisole, heptane, butyl butyrate, and hexyl butyrate, preferably p-xylene; and the organic solvents in the first slurry and the second slurry are the same or different.

7. A method for preparing a 3D printed lithium-ion battery negative electrode sheet, characterized in that: The following steps are involved: (1) mixing a silicon-based material and / or a hard carbon material and a binder in an organic solvent to obtain a slurry; and passing the slurry into a 3D printer syringe pump; (2) performing 3D printing on the current collector using a 3D printer to obtain a first 3D printed layer and a second 3D printed layer; wherein the first 3D printed layer includes a structural unit obtained by printing the slurry and a gap unit; and a second 3D printed layer is obtained by printing the slurry on the first 3D printed layer; (3) The material after 3D printing is dried to obtain the 3D printed lithium-ion battery negative electrode sheet.

8. The method for preparing a 3D printed lithium-ion battery negative electrode sheet according to claim 7, wherein: The mass ratio of the silicon-based material and / or hard carbon material to the binder in the slurry is (18-20):1, preferably 19:1; And / or, the extrusion pressure of the 3D printer is 0.01-0.05 MPa, and the printing speed is 100-500 mm / s; And / or, the drying treatment includes first drying at 50-80° C. for 20-40 min, and then vacuum drying at 75-85° C. for 10-24 h.

9. The method for preparing a 3D printed lithium-ion battery negative electrode sheet according to claim 7, wherein: The first 3D printing layer and the second 3D printing layer are respectively single material layers of a silicon-based material layer or a hard carbon material layer; Preferably, the first 3D printing layer is a silicon-based material layer; the second 3D printing layer is a hard carbon layer; More preferably, when the first 3D printing layer is a silicon-based material layer and the second 3D printing layer is a hard carbon layer, The thickness of the structural unit after being covered by the second 3D printed layer is d1, and the thickness of the gap unit after being covered by the second 3D printed layer is d2, wherein d2≤d1, preferably d2<d1; Preferably, in the first 3D printing layer, the spacing between adjacent gap units is 0.8 to 1.3 mm; the total area of ​​the gap units accounts for 13% to 20%; the difference between d1 and d2 is 10 μm to 30 μm; Preferably, the spacing between adjacent gap units is 0.8 to 1 mm, preferably 1 mm; Preferably, the total area of ​​the void units accounts for 13% to 17%, more preferably 15% to 17%, and even more preferably 17%; Preferably, the difference between d1 and d2 is 10 μm to 20 μm, more preferably 20 μm; and / or, the structural units are connected to form a honeycomb shape, a concentric ring shape, an Archimedean spiral shape, a parallel line shape, a parallel wavy line shape or a Heber curve shape, preferably a honeycomb shape; And / or, the silicon-based material includes at least one of micron silicon, porous silicon, amorphous silicon, and silicon-oxygen composite materials, Preferably micron silicon; And / or, the current collector is copper foil or copper-lithium composite tape; preferably copper-lithium composite tape; And / or, a solid electrolyte layer is provided on the surface of the negative electrode of the battery; Preferably, the binder comprises hydrogenated nitrile rubber, nitrile rubber, carboxyl nitrile rubber, butadiene rubber, At least one polyisobutylene rubber; preferably hydrogenated rubber; Preferably, the organic solvent includes at least one of p-xylene, toluene, anisole, heptane, butyl butyrate, and hexyl butyrate, preferably p-xylene.

10. A lithium-ion battery, electrochemical device, or energy storage device, characterized in that: A 3D printed lithium-ion battery negative electrode sheet comprising any one of claims 1 to 6, or a 3D printed lithium-ion battery negative electrode sheet prepared by the preparation method according to any one of claims 7 to 9; Preferably, the lithium-ion battery is an all-solid-state battery.

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